Electromagnetic Spectrum

Posted By: technopediasite



Introduction

EMR is radiation made up of oscillating electric and magnetic fields and propagated with the
speed of light. EMR includes gamma radiation, X rays, ultraviolet (UV), visible, and infrared
(IR) radiation, as well as radar and radio waves. The frequency or electromagnetic spectrum is the range of frequencies of EMR from zero to infinity.

Spectrum Groups

The electromagnetic spectrum was, by custom and practice, formerly divided into 26
alphabetically designated bands. This usage still prevails to some degree. However, the
International Telecommunication Union (ITU) recognizes 12 bands, from 30 Hz to 3000 GHz.New bands, from 3 THz to 30 THz, are under consideration for recognition.

• Radio waves

– Extremely low frequency (ELF) = 30 to 300 Hz

– Voice frequency (VF) = 300 Hz to 3000 Hz

– Very low frequency (VLF) = 3 KHz to 30 KHz

– Low frequency (LF) = 30 KHz to 300 KHz

– Medium frequency (MF) = 300 KHz to 3 MHz

– High frequency (HF)—HF radio = 3 MHz to 30 MHz

– Very high frequency (VHF)—FM radio = 30 MHz to 300 MHz

– Ultrahigh frequency (UHF)—cellular and trunk radio = 300 MHz to 3000 MHz

– Super high frequency (SHF)—radar and microwave radio = 3 GHz to 30 GHz

– Extremely high frequency (EHF)—microwave and satellite = 30 GHz to 300 GHz

– Submillimeter waves = 300 GHz to 3000 GHz (or 3 THz)

– Far-infrared = 3000 GHz to 30,000 GHz (or 3 THz to 30 THz)

• Visible light

• UV light

• Soft X ray

• Hard X ray

• Gamma ray